Increased Toll-like receptor (TLR) mRNA expression in monocytes is a feature of metabolic syndrome in adolescents

Background: Metabolic syndrome (MetSyn) is diagnosed frequently in some but not all overweight adolescents. Chronic inflammation, as seen in obesity, is strongly associated with MetSyn. Objectives: The aim of this pilot study was to assess the correlation between activation of the innate immune system and MetSyn, independent of body mass index (BMI), in a young population. Methods: We quantitatively measured both systemic pro-inflammatory cytokines and gene expression of Toll-like receptors (TLRs) and downstream cytokines in circulating monocytes obtained from nine adolescents with metabolic syndrome (Overwt-MetSyn) and eight BMI-matched controls (Overwt-Healthy). Results: The Overwt-MetSyn group demonstrated a significant elevation in expression of TLR2, TLR4, tumour necrosis factor-a (TNF a) and interleukin-6 (IL6) in peripheral monocytes, and increased circulating levels of TNF a and IL6 when compared with the Overwt-Healthy group. TLR2 (r = 0.78, P < 0.001), TLR4 (r = 0.57, P < 0.01) and TNF a (r = 0.61, P < 0.01) gene expression positively correlated with serum levels of TNF a. Conclusions: Our study suggests that activation of the innate immune pathway via TLRs may be partially responsible for the increased systemic inflammation seen in adolescents with MetSyn.